1. Field of the Invention
Automatic identification systems using radio/microwaves (RFID=Radio Frequency Identification) are characterized by identification devices (also designated ID tags, data carriers, cards, transponders, etc.) attached to the object to be identified and read from a remote location with the aid of a reader. The objects often pass in an ordered stream or flow, such as chassis and their manufacture in a car manufacturing plant, containers in different distribution systems, cars that have access to garages and restricted areas, people passing through highly frequented doors and passage gates, trucks in distribution centers, ports, airports and the like, railway traffic along a railroad track, and so on.
2. Description of the Related Art
A range of several meters is achieved with microwave based systems, which often operate in the bands of 915 MHz, 2.45 GHz and 5.8 GHz, which is particularly suitable for the aforementioned relatively large objects. In this regard, stationary reading units are placed adjacent the locations which the objects are expected to pass, so that identification can be effected fully automatically.
One problem, however, is that the objects do not always move in a steady stream or flow, but are parked, stopped, or take routes other than those expected. Consequently, it is desirable to obtain a compact and portable reading unit that can be readily placed in the vicinity of the object to be identified, e.g., a load carrier that awaits further transportation.
Further transportation to superordinate systems also represents a problem. A portable unit cannot, after all, simply be connected via a cable for the transfer of data from the ID devices. Similarly, if the ID device is of a programmable type, very simple transmission of data from superordinate systems to the portable unit and from there to the data carrier is desired.
Patent Application WO 93/16351 A1 provides a solution to these problems. Although this unit is portable and solves the aforesaid problems, its practical design is particularly expensive to produce. This is because the market requirement of portable units constitutes only a hundredth of the requirement for stationary units. Such units are also relatively clumsy, because the small series in which they are produced do not permit a sufficiently high integration level, i.e., discrete components are used instead of ASIC's, standard designs must be used with regard to casings, displays, keybanks, etc., and the functionality of such units is also restricted because of the lack of standards for the wireless communication with superordinate systems.